A package for sterile objects, which are used by a surgeon, is known from U.S. Pat. No. 4,437,567. It is stated therein that the package may be made of conventional materials such as a plastic coated metal, glass, plastic film or sheet, plastic coated metal foil or metallized paper or other packaging material impervious to liquid and inert to contents of the package. From British Pat. No. 1,263,217 a packaging material is known for packaging sutures which may be used in surgery, whereby it is important that the sutures prepared from polyglycolic acid are packed in dry conditions and that during storage no moisture penetrates into the package; such moisture would attack the suture of polyglycolic acid and strongly reduce its usability.
The invention is especially directed to finding a packaging material for electrodes whereby the packaging material can also be used to package welding flux, welding wires and backing-up strips or other comparable objects.
Electrodes which do not have to meet special requirements are packed in cardboard boxes, as is available on the market, whilst electrodes which need to be stored under dry circumstances are packed in hermetically sealed cans. Therefore, the invention especially relates to a packaging material to package electrodes which up to now were stored in tins, said electrodes being of a type such as described in the British patent application No. 2,070,976, titled: "Process for production of a low hydrogen type covered arc-electrode".
Low hydrogen covered electrodes are used for welding operations where high standards are set for the welding material in welded joints in structural steel kinds such as Fe E355 or Fe E450, such as are used in, for example, offshore oil and gas producing platforms. One of the standards to be met thereby is that the electrode to be used has a low moisture content, preferably a moisture content so low that the quantity of hydrogen in the welding metal is less than 5 ml per 100 g of melted down welding metal. Customary instructions in connection with thick-walled, rigid constructions require the redrying of coated electrodes at a temperature of 300.degree.-400.degree. C. when the electrodes are supplied in a package which is not completely moisture-proof. Further, it is necessary for coated electrodes to be stored in a dry atmosphere after the redrying treatment, which can be achieved, for example, in warm storage cabinets or tubes at a temperature of about 75.degree.-150.degree. C. It cannot be assumed that these instructions are carried out completely and accurately. These operations also cause important substantial labour expenses. The absorption of moisture by coated electrodes before welding of the electrodes may lead to an undesired high level of diffusable hydrogen, as a result of which the risk of cracks initiated by hydrogen is present in the heavy and rigid steel constructions mentioned above.
A moisture-proof package which has been used so far in this field is a hermetically sealed can, but such a package of tinplate usually contains about 25 kg of electrodes; this corresponds to 400-500 electrodes, which cannot be processed within a time span of 4 hours by a welder. Therefore, it is necessary for the electrodes from such a can to be stored in the above-mentioned warm storage cabinets or tubes when the can has been open longer than 4 hours.
Efforts have been made, therefore, to find a material for a package unit which contains such a number of electrodes as a welder will use within four hours, and the package covers the electrodes and maintains the low moisture content the electrodes originally have in the unopened package. During long storage in the package the moisture content of the packed electrodes should not increase. This will do away with drying and warm storage before use of the electrodes if the electrodes are used within a few hours, viz. within about 4 hours after the package has been opened.
Another problem which occurs when electrodes and the like are packed in a package which must contain relatively heavy electrodes is the mechanical strength of the packaging material that provides moisture-proof storage. These requirements with regard to the mechanical strength are of no influence or play hardly any role with the packaging material which is described in British Pat. No. 1,263,217 in which a packaging material is disclosed to package sutures moisture-proof.